Experimental study of repaired RC columns subjected to uniaxial and biaxial horizontal loading and variable axial load with longitudinal reinforcement welded steel bars solutions

The study of the reinforced concrete (RC) columns' response to horizontal cyclic loads is of full importance to understand how earthquakes affect the integrity of structures. Essentially those already built and especially vulnerable to this type of action, as is the case of many existing buildings on significant seismic activity zones which are not adequately prepared for that eventuality. Consequently, there is also the need to perform a significant number of studies of repairing procedures of structural elements, so as to restore its function and possibly achieve an improvement in relation to its original seismic resistance. The present experimental work is focused in the study of welding joints for steel bars used in building columns, supported by tensile tests on specimens according to the actual welding regulations. The experimental results are analyzed and discussed with particular attention to the specimens' behaviour in terms of strength and ductility compared to the results obtained for original steel bars. After the definition of the proper welding solution, six RC columns previously tested were repaired and retrofitted with this solution tested under uniaxial and biaxial horizontal loading and variable axial load in order to compare the global result with the original tested columns and the effects introduced by the repair process.